Cryogenic pressure switch



Aug. 8, 1967 J. G- MEJEAN ETAL CRYOGENIC PRESSURE SWITCH Filed Oct. 4, 1965 F igure Compensal/n g Pressure ET00/npensa//ng Bellows *F/ex Plate [System For] INVENTORS Jacques 6. Mejean Emanuel J. Df/Voia Theodore A. Bram/ch BY- United States Patent Office ware Filed Oct. 4, 1965, Ser. No. 492,828 8 Claims. (Cl. 200-140) The present invention is directed to an improved form of pressure switch and more particularly to a switch design and construction which is adapted to operate under high vibration and low temperature conditions.

The usual types of pressure switches embody the use of bellows members or other types of pressure sensitive flexible diaphragm means so as to have an activating member working responsive to a variable pressure system; however, the conventional pressure switches do not utilize adjustment means to compensate for changes in modulus of elasticity under low temperature conditions. Also, usual pressure switch constructions do not provide electrical switching means in combination therewith which will provide vibration free make and break contacts. For example, a usual flexible arm or snap action type of switch has an inherent weakness to the resistance of vibration in the switching arm.

It is thus a particular feature of the present improved pressure switch design to provide special springing and alignment means in connection with an actuating bellows or flexible diaphragm, as well as the utilization of a special movable ball magnetic type of switch means in combination therewith'to provide a positive operation. A magnetic type of switching means or latching relay precludes the desired circuit from being broken or interrupted by reason of vibrations in the switch arm or from the diaphragm assembly and, in addition, can operate to advantage at low temperature conditions.

It is also a feature of the present improved assembly to utilize a combination dash-pot member and compensating bellows positioned in alignment and in contact with the actuating diaphragm or bellows member of the unit so as to obtain some degree of damping of vibration which will more readily occur for operations at very low temperature conditions. At the same time, the improved assembly provides compensation for changes in modulus of elasticity in the moving parts of the device, such as the actuating diaphragm and accompanying spring, etc.

Briefly, the present improved cryogenic pressure switch embodies a construction and arrangement which comprises in combination, a flexible actuating diaphragm held within a confined housing, an actuating fluid pressure inlet to said housing positioned to provide communication with one side of said diaphragm, compressive spring means connecting to and opposing the action of said flexible diaphragm, shaft means extending from a central movable portion of said diaphragm to connect with and actuate a switch arm, with the latter being positioned to move between spaced electrical contact points responsive to pressure changes in said diaphragm, said contact points for said switch arm connecting with a magnetic ball relay of single pole, double throw type for latching in both operating positions of said switch arm, and a second flexible diaphragm positioned in said housing to close a confined dash-pot zone and to contact said shaft means whereby to oppose the action of said actuating diaphragm for modulus of elasticity compensation and to damper it against vibrations.

A preferred construction of the present switch assembly integrates a means for readily calibrating the device by checking the electrical switching responsive to various Patented Aug. 8, 1967 test pressures. Such calibration means will provide for overcoming the spring action of the bellows member, or diaphragm, and its opposing spring means so that a check may be made of the tolerance or movement of the bellows response to different pressure settings. For example, one form of calibrating means combinable with the pressure switch device involves the use of a separate calibrating bellows that is positioned to permit contact with the actuating system bellows, so that after compressing the calibrating bellows with a released system bellows there may be effected the displacement of the latter responsive to different pressures being introduced through a calibration port to the calibration bellows. Another calibration arrangement, which may be integrated with the system bellows in the device, utilizes a dual section calibrating bellows, with one section of the latter having an enlarged area so as to compensate for the spring action of the systems bellows.

The design and construction of the present improved cryogenic pressure switch, together with modifications which may be embodied into a preferred design, will be better understood by reference to the accompanying drawing and the following description thereof.

FIGURE 1 of the drawing is a diagrammatic sectional view showing the design and construction of a pressure sensitive actuating means and preferred guide and spring means in combination therewith, as well as a preferred form of electrical switching means.

FIGURE 2 of the drawing shows, in a partial sectional view, a modified arrangement which may be utilized to effect the testing and calibrating of the flexible bellows portion of the switch.

FIGURE 3 of the drawing also shows, in a partial sectional view, an alternative calibrating arrangement for use with the pressure sensitive device.

Referring now particularly to FIGURE 1 of the drawing, there is shown a housing 1 adapted to support an internally positioned bellows member 2 which can operate responsive to a variable pressure system communicating to the interior of housing 1 through port means 3. The bellows 2 connects with an axial stem 4 which has a transverse spring holding member 5 and then continues on to terminate in a suitable guided connection with the end of a flexible plate or arm member 8. The latter may have a hole or slot to pass around the stem 4 between suitable enlarged hub-like sections thereon. The flexible plate means 8 is suitably connected with the interior side portion of housing 1 at 9 so to provide the desired movable guide or alignment means for the top end of the stem 4. The transverse member 5 from stem 4 in turn holds and supports an axially positioned compression spring member 6 within the central portion of housing 1. A suitable transverse partition-like section 7 across the interior of the housing serves to hold the opposite end of the spring 6. There is also provided an intermediate movable flexible plate or arm 10 connected to the interior of the housing at 11 for providing additional alignment of the stem 4 as it is moved axially responsive to pressure changes and resulting expansions and contractions of the bellows 2.

A preferred form of compression spring 6 is of the cantilever spring construction with opposing interconnecting cantilevering sections, such as indicated in the drawing, so as to eliminate any torsional effects on the bellows member as the end of the latter moves in response to pressure changes and the spring in turn compresses or is extended. It should also be noted that it is preferable to utilize a multiple convolution bellows member 2 in lieu of a single flexible diaphragm member, since for a given diameter and for a given variation of pressure the multiple section bellows member will provide more movement or axial travel than a single diaphragm. Also, the end face of a bellows member, such as 2, may be made flat in order to more readily accommodate means for testing and calibrating the completed device. Still further, it is preferable that the bellows member, and all movable internal members connected therewith, shall be made of one type of alloy metal so that all parts will have the same coefficient of expansion and there will be minimization of the effects of variations in temperature.

In the present embodiment of the pressure sensitive switch device, the electrical circuit or switching means is activated by the movement of a switch arm 12 which is bolted or otherwise connected to the flexible plate member 8 at the top of the axially positioned stem member 4. The free end of the switch arm 12 is movable between contact points 13 and 14 responsive to the expansion and/or retraction of bellows member 2 which, of course, moves responsive to pressure changes within the closed end portion 15 of housing 1. That portion of the interior of the housing 1 which supports the cantilever spring 6 and the switch arm member 12 may be left open to the atmosphere so that there is pressure equilizatio-n therein or, conversely, such interior portion may be placed under vacuum within a closed housing, depending upon whether or not it is desired to have calibrating means for adjusting and testing the bellOWs operating switch that will require an internal vacuum situation.

Again referring to the embodiment of FIGURE 1, it will be noted that the upper end portion of the housing 1 is provided with a separately enclosed pressure zone 16 suitable for holding a gas under pressure to serve as a dash-pot zone and, in addition, a transverse dash-pot member 17 joining with an upper stem member 18. The latter extends axially through a compensating bellows 19 to terminate in an end section 20 which is adapted to contact the switch arm 12 at a point opposite the end of lower stem 4. The interior of the dash-pot 16 is in open communication with the interior of the bellows 19 so as to maintain a compensating pressure therein to assist in overcoming the effects of temperature on the modulus elasticity of the bellows member 2 and spring member 6. A suitable port means 21 with plug member 22 provides access for introducing a gas under pressure into the dashpot zone 16.

Inasmuch as the bellows, stem, and spring assembly will be subjected to high vibrations under low temperature conditions it is particularly desirable to achieve some measure of stabilization by a dash-pot effect. As previously set forth, the bellows stem will be guided by flexplates 8 and 10 so as to maintain the bellows parallel to itself and not effect any side motion thereof. The flexplates are substantially frictionless in their operation and are not susceptible to the same wear as would be encountered with conventional shaft guiding means under vibration conditions.

In connection with the dash-pot zone 16 and plate 17, it may be noted that a usual dash-pot arrangement with a low pressure fluid or gas would not Work satisfactorily under extremely low temperature conditions which may be down to the order of 400 F. In other words, after the temperature falls there would not be enough effect from the pressure of the gas placed in the dash-pot under normal atmospheric conditions. On the other hand, by the utilization of a small bellows, such as 19, which has an effective cross-sectional area substantially less than that of the systems bellows 2, then there may be a higher pressure utilized in the dash-pot zone 16 by a factor of the ratio of the area of bellows 2 with respect to the bellows 19. Stated another way, where the effective area of bellows 19 is a fractional portion of the area in bellows 2 in the ratio l/ n and the pressure within the bellows 19, as well as in dash-pot zone 16, is maintained at n-times the operating pressure of the system from port 3, it is possible to maintain a modulus of elasticity compensation. At the same time, there may be utilized an enlarged area dash-potting piston 17 which will serve to dampen the vibration effects encountered from the bellows 2, spring 6, and various members connecting along the length of the stem means.

Referring now to the electrical switching portion of the device, as shown diagrammatically as a part of FIG- URE 1, there is indicated an electrical lead 23 from contact of 13 to a coil 24 passing around a soft iron core member 25 and terminating with a magnetic bar member 26. An electrical lead from contact point 14 also connects with an electrical coil 28 which also circumscribes an end portion of the center core member 25 and then terminates in contact with a magnetic bar 29. The latter is positioned to have its north and south poles to oppose those of magnetic bar 26. The resulting arrangement of the two magnets 26 and 29 on each side of a soft iron core member 25 results in a magentic relay which may be designated as a single pole, double throw system, latching in both operating positions. A movable ball member 30 is held at one end of the soft core member 25 so as to be able to move or alternate in positions between the opposing north and south poles of the opposing magnets 26 and 29. Thus, in operation the movable ball 30 serves to complete a circuit and carry current from lead A to lead C or, alternatively, carry current between lead A and lead B. For example, where the switch arm 12, as actuated by the stem from bellows 2, touches the contact point 14 there is an energizing of the coil 28 on the core member 25 with the result that the ball member 30 is attracted to the north pole end of magnet 26 and becomes a part of the magnetic circuit between the latter and core 25 carrying current from lead A to lead B. As the ball transfers, it breaks the circuit A to C and deenergizes coil 28. Because of the magnetic effect, ball 30 will remain in this position regardless of vibrtaion effects until coil 24 is energized. The disconnection of coil 28 eliminates arcing if contact 14 vibrates and also keeps coil 23 from overheating due to excessive current at low temperature. Similarly, where bellows 2 moves to change the positioning of switch arm 12 such that it touches contact 13 and energizes coil 24 there is a resulting north pole occurring at the upper end of core member 25 so that ball 30 will be repelled from the end of the magnet 26 and pulled into contact with the south pole of magnet 29. This position will complete a current carrying circuit between leads A and C. The completion of circuit A and C opens circuit A and B which disconnects coil 24. The ball keeps circuit A and C closed, due to the attraction of the magnetic pole, until coil 28 is energized. Subsequently, when current is sent through coil 28, the reverse action will take place in polarity of core 25 and the ball 30 will revert to it soriginal position in contact with the end of magnet 26. It should be noted that the particular advantage of the present type of switching or relay type means results in a positive, non-intermittent type of circuitry. In addition, there are no difficulties encountered because of low temperature conditions. In other word, this circuitry is such that after an impulse has been sent to either of the energizing coils and there is a transfer of the ball member 30, then a particular circuit is held without any power being drawn and the coil disconnected so that contact arcing and coil heating is eliminated. The circuit does not transfer or draw power until the opposite contact point is touched and the subsequent transfer repeats the procedure on the opposite circuit. This may of course be done with low electrical impulses of the order of 5 to 10 milliamperes and obtain satisfactory results.

As indicated hereinbefore, various means may be provided for integrating suitable in place calibration devices with the present pressure sensitive means. In FIGURE 1 of the drawing, there is merely shown a calibration port 31 and with plug means 32 such that there may be access for connecting a test pressure source or for placing a calibration device into contact with the actuating bellows 2. However, with reference to FIGURE 2 of the drawing, there is shown one form of in place calibration device that may be used to check the settings or tolerance of the bellows 2 and the switching circuitry responsive to various test pressures. Calibration should of course be achieved without utilizing the system port 3 or by any direct use of the system bellows 2. Further, it is advisable to utilize a separate calibration bellows, the displacement of which can be transmitted directly to the system bellows. In FIGURE 2, there is a calibration bellows 33 welded or otherwise connected and sealed to an adjustable bushing 34 and that in turn is threadedly engaged within a threaded opening in the lower end of a housing 1. The bellows 33 is of the same size and area as the actuating bellows 2 and is installed so that it is in close proximity to the end face of system bellows 2. The enclosed space between the interior of bellows 33 and bushing 34 is accessible through a test pressure port 35 having a removable plug member 36. The systems pressure for the normal actuation of bellows 2 is introduced through port 3'. In effecting the calibration or adjustment of the pressure sensitive device, the bushing member 34 is turned in a manner to effect the touching of bellows 33 at the bottom of the system bellows 2', with the latter being in an upper operating position responsive to system pressure from port 3' whereby the stem 4 would be effecting a contact between a raised switch arm and an upper electrical contact point. (The latter is not shown in the drawing.) Then, when the systems pressure is released there will be an expansion of bellows 2' causing a compression of the calibrating bellows 23. In this position, there may be test pressure through port 35 to check the movement of bellows 2, stem 4' and the operation of the switch arm to energize the electrical switching means. The result of this form of calibration is, of course, the elimination of the spring action of the calibration bellows 33 since it is at its free length, and test pressures on the interior of 33 will provide equivalent pressures to that of the activating pressures on the bellows 2'. Generally, in reflecting the calibration of a device such as this, it is desirable to test and calibrate for either an increasing or decreasing pressure and, as heretofore described, the calibration has been illustrated for an increasing pressure. In other words, test pressures are applied to the calibrating bellows after the actuating bellows is at a free length whereby the switch is being checked on increasing pressures through the calibration bellows 33 as equivalents to system pressure against the outside of the activating bellows 2'. Unless the device is calibrated against decreasing pressure operations, and averaged with the calibrations for increasing pressures there will be some discrepancy occurring between actuating pressures recorded with respect to decreasing test pressures at the calibration port.

In a modified calibration system which may be advantageously integrated with the pressure sensitive device, as illustrated in FIGURE 3 of the drawing, there is an arrangement which will provide accuracy for both increasing and decreasing pressure readings. Specifically, there is shown a housing 1" containing a bellows 37 which is of larger area and diameter than bellows 2" and a bellows 38 which is the same size and diameter as 2". Bellows sections 37 and 38 are fixedly linked together by a stem member 39 and the interior space 40 between the two bellows sections is evacuated to provide a vacuum situation. A calibration pressure is introduced into the housing 1" through port 41 having a removable plug member 42. It will be seen that in effecting the calibration of this arrangement that the calibration pressure as applied to the larger bellows 37 will effect a net pressure which is the difference in area between the bellows 37 and 38 and thus provide a cancellation of the effect of the spring action of actuating bellows system.

In arriving at the difference in area or size between bellows 37 and 38 it is necessary to calculate a difference which will provide an equivalent for the spring action of the bellows 38 or its equivalent 2". Bellows 38 will of course have an equivalent diameter and number of convolutions to that of bellows 2" in order to have the same spring rate as the latter. In effecting the compensation for the spring rate of the bellows 2", then the upper flat face of bellows 38 can be brought into contact with the face of bellows 2'. and various test pressure then applied to the larger bellows 37 to check action of the stern member 4" which in turn will actuate the electrical switching means of the unit. It may also be noted in connection with the design and construction of FIGURE 3 that there is a double metal wall existing between the calibration port 41 and the system bellows 2" so that if there was a rupture of one of the two bellows 37 or 38 there would be no leakage of the system pressure existing in the zone around bellows 2" from port 3".

It may be pointed out that the constructions of the device shown diagrammatically in the present drawing shall not be limiting and that there may be various modifications with respect to the sizing and means of fabricating or constructing individual parts for assembly purposes. Preferably, all of the bellows members shall be carefully welded and sealed with the various pertinent portions of the housing or bushings in order that there is no leakage in the housing. The housing may of course be made in a number of ways in order to accommodate the installation or assembly of various internal parts. The switching and relaying means is also diagrammatic and may be encased or housed in various manners in combination with the pressure sensitive portion of the unit. The unit may be positioned horizontally or angularly and need not be in the vertical position illustrated. Thus, the terms upper and lower as used in the present description are merely relative to the present drawing.

We claim as our invention:

1. A pressure switch providing resistance to vibrations and to low temperature conditions, which comprises in combination, a flexible actuating diaphragm held within a confined housing, an actuating fluid pressure inlet to said housing positioned to provide communication with one side of said diaphragm, compressive spring means connecting to and opposing the action of said flexible diaphragm, shaft means extending from a central movable portion of said diaphragm to connect with and actuate a switch arm, with the latter being positioned to move between spaced electrical contact points responsive to pressure changes on said diaphragm, said contact points for said switch arm connecting with a magnetic ball relay of single pole, double throw type for latching in both operating positions of said switch arm, and a second flexible diaphragm positioned in said housing to enclose a confined dash-pot zone, a fluid medium in said dash-pot zone, contact means from said second flexible diaphragm to be connective with said shaft means whereby to oppose the action of said actuating diaphragm for modulus of elasticity compensation and to damp it against vibrations.

2. A pressure switch providing resistance to vibrations and to low temperature conditions, which comprises in combination, a flexible actuating bellows member held within a confined housing, an actuating fluid pressure inlet to said housing positioned to provide communication with an exterior portion of said bellows member,

a cantilever form of compressive spring means connective with and opposing the action of said flexible bellows member, shaft means extending from a central movable portion of said bellows member to connect with and actuate a switch arm, with the latter being positioned to move between spaced electrical contact points responsive to pressure changes on said bellows member, said contact points for said switch arm connecting with a magnetic ball relay of single pole, double throw type for latching in both operating positions of said switch arm, and a second flexible bellows member positioned in said housing and closing a confined dash-pot zone at the end of said housing, a movable transverse dash plate in said dash-pot zone and connected with a movable free end of said second bellows member means from the latter arranged to oppose first said shaft means whereby to oppose the action of said actuating bellows member for modulus of elasticity compensation and to damp it against vibrations.

3. The pressure switch of claim 2 further characterized in that second bellows member for enclosing said dashpot zone has a substantially smaller cross sectional area than said actuating bellows whereby an inversely proportioned increased pressure fluid medium may be retained in such zone around said transverse dash plate.

4. The pressure switch of claim 2 further characterized in that said shaft means extending from said actuating bellows is connective with flexible-plate guide means extending from an interior side wall port-ion of said hous- 5. The pressure switch of claim 2 further characterized in that said bellows members, said compression spring, said shaft and flexible plate guide means are formed of the same type low temperature resistant alloy metal whereby to minimize effects of coefiicient of expansion of said internal parts.

6. A unitary pressure switch construction providing resistance to vibrations and to low temperature conditions and having in place calibration means integrated therewith, which comprises in combination, a flexible actuating bellows member held within a confined housing, an actuating fluid pressure inlet to said housing positioned to provide communication with an exterior portion of said bellows member, a cantilever form of compressive spring means connective with and opposing the action of said flexible bellows member, shaft means extending from a central movable portion of said bellows member to connect with and actuate a switch arm, with the latter being positioned to move between spaced electrical contact points responsive to pressure changes on said bellows member, said contact points for said switch arm connecting with a magnetic ball relay means of single pole, double throw typefor latching in both operating positions of said switch arm, a second flexible bellows member positioned in said housing and closing a confined dash-pot zone positioned at the end of said housing, a movable transverse dash plate in said dash-pot zone and connected with a movable free end of said second bellows member, and means from the latter arranged to oppose first said shaft means whereby to oppose the action of said actuating bellows member for modulus of elasticity compensation and to damp it against vibrations, calibration means positioned within the end of said housing opposing the external movable face of said actuating bellows, with said calibration means incorporating at least one calibrating bellows section of equal area and of equal convolutions to said actuating bellows member which can contact the latter, and said calibration means further having test pressure inlet port means thereto to cause movement of said calibrating bellows and of said actuating bellows member, whereby the-re may also be movement of said connecting shaft means and said switch arm for a calibration check of the electrical relay means responsive to different calibration test pressures.

7. The pressure switch construction of claim 6 further characterized in that said calibration means comprises, a bushing member having position adjustments connecting it with the end of said housing, a calibrating bellows member of equal diameter and of equal member of convolutions as said actuating bellows mounted on and sealed to an interior face of said bushing and leaving a calibrating pressure zone therebetween, with said calibrating bellows having a face portion adapted to oppose and touch an internal face of said actuating bellows, and test pressure port means through said bushing to provide calibrating pressure in said zone within said calibrating bellows.

8. The pressure switch construction of claim 6 further characterized in that said calibration means comprises, an enclosed dual section calibrating bellows assembly, with one section of equal diameter and of equal number of convolutions as said actuating bellow-s and a second section wit-h an enlarged area with respect to said actuating bellows, said enlarged area proportioned to balance the spring action of said actuating bellows and of the additional members connective therewith between the latter and said electrical relay means, the juncture between said dual bellows sections connected with and sealed to the interior of said housing in a position to have the equal sized face of the calibrating bellows section oppose and permit contact with the outer face of the actuating bellows, rigid connector means internally connecting the movable end face portions of said dual section calibrating bellows together to make them move in unison, a subatmospheric pressure provided within said enclosed calibracing bellows, and test pressure port means to said housing positioned to act externally on said enlarged area section of the calibrating bellows.

References Cited UNITED STATES PATENTS 1,820,063 3/1931 Geiler 200-815 2,044,729 6/ 19 36 Eggleston et al. 200-81.5 2,498,864 2/1950 Root 2s6 -51 3,194,915 7/1965 Andersen 200-83 BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Examiner. 

1. A PRESSURE SWITCH PROVIDING RESISTANCE TO VIBRATIONS AND TO LOW TEMPERATURE CONDITIONS, WHICH COMPRISES IN COMBINATION, A FLEXIBLE ACTUATING DIAPHRAGM HELD WITHIN A CONFINED HOUSING, AN ACTUATING FLUID PRESSURE INLET TO SAID HOUSING POSITIONED TO PROVIDE COMMUNICATION WITH ONE SIDE OF SAID DIAPHRAGM, COMPRESSIVE SPRING MEANS CONNECTING TO AND OPPOSING THE ACTION OF SAID FLEXIBLE DIAPHRAGM, SHAFT MEANS EXTENDING FROM A CENTRAL MOVABLE PORTION OF SAID DIAPHRAGM TO CONNECT WITH AND ACTUATE A SWITCH ARM, WITH THE LATTER BEING POSITIONED TO MOVE BETWEEN SPACED ELECTRICAL CONTACT POINTS RESPONSIVE TO PRESSURE CHANGES ON SAID DIAPHRAGM, SAID CONTACT POINTS FOR SAID SWITCH ARM CONNECTING WITH A MAGNETIC BALL RELAY OF SINGLE POLE, DOUBLE THROW TYPE FOR LATCHING IN BOTH OPERATING POSITIONS OF SAID SWITCH ARM, AND A SECOND FLEXIBLE DIAPHRAGM POSITIONED IN SAID HOUSING TO ENCLOSE A CONFINED DASH-POT ZONE, A FLUID MEDIUM IN SAID DASH-POT ZONE, CONTACT MEANS FROM SAID SECOND FLEXIBLE DIAPHRAGM TO BE CONNECTIVE WITH SAID SHAFT MEANS WHEREBY TO OPPOSE THE ACTION OF SAID ACTUATING DIAPHRAGM FOR MODULUS OF ELASTICITY COMPENSATION AND TO DAMP IT AGAINST VIBRATIONS. 